Flash 8 ActionScript 2.0 Language Reference

Class Function

Object

apply Method

public apply(thisObject:Object, [argArray:Array]) : Void

The parameters are specified as an Array object, unlike Function.call(), which specifies parameters as a comma-delimited list. This is often useful when the number of parameters to be passed is not known until the script actually executes.

Returns the value that the called function specifies as the return value.

Math.atan2(1, 0)
Math.atan2.apply(null, [1, 0])

The following simple example shows how apply() passes an array of parameters:

function theFunction() {
    trace(arguments);
}

// create a new array to pass as a parameter to apply()
var firstArray:Array = new Array(1,2,3);
theFunction.apply(null,firstArray);
// outputs: 1,2,3

// create a second array to pass as a parameter to apply()
var secondArray:Array = new Array("a", "b", "c");
theFunction.apply(null,secondArray);
// outputs a,b,c

The following example shows how apply() passes an array of parameters and specifies the value of this:

// define a function 
function theFunction() {
    trace("this == myObj? " + (this == myObj));
    trace("arguments: " + arguments);
}

// instantiate an object
var myObj:Object = new Object();

// create arrays to pass as a parameter to apply()
var firstArray:Array = new Array(1,2,3);
var secondArray:Array = new Array("a", "b", "c");

// use apply() to set the value of this to be myObj and send firstArray
theFunction.apply(myObj,firstArray);
// output: 
// this == myObj? true
// arguments: 1,2,3

// use apply() to set the value of this to be myObj and send secondArray
theFunction.apply(myObj,secondArray);
// output: 
// this == myObj? true
// arguments: a,b,c

call Method

public call(thisObject:Object, [parameter1:Object]) : Object

In almost all cases, the function call (()) operator can be used instead of this method. The function call operator produces code that is concise and readable. This method is primarily useful when the thisObject parameter of the function invocation needs to be explicitly controlled. Normally, if a function is invoked as a method of an object, within the body of the function, thisObject is set to myObject, as shown in the following example:

myObject.myMethod(1, 2, 3);

In some situations, you might want thisObject to point somewhere else; for example, if a function must be invoked as a method of an object, but is not actually stored as a method of that object:

myObject.myMethod.call(myOtherObject, 1, 2, 3); 

You can pass the value null for the thisObject parameter to invoke a function as a regular function and not as a method of an object. For example, the following function invocations are equivalent:

Math.sin(Math.PI / 4)
Math.sin.call(null, Math.PI / 4)

Returns the value that the called function specifies as the return value.

function myObject() {
}
function myMethod(obj) {
    trace("this == obj? " + (this == obj));
}
var obj:Object = new myObject();
myMethod.call(obj, obj);

this == obj? true